A freedom of information request submitted by the BBC found no mystery shopping exercises had been carried out since March 2010.
In 2010, FSA chief executive Sants said he would step up mystery shopping exercises.
Consumer groups said they found the news “surprising”.
“It is a little surprising that the FSA hasn’t placed more of an emphasis on mystery shopping, which can be a useful tool in identifying consumer detriment,” Sarah Brooks, director of financial services at Consumer Focus, told the BBC.
“We accept that mystery shopping may not provide the hard evidence needed for enforcement action. However, it can act like a canary in a mineshaft – an indicator of problems.”
An FSA spokesperson said: “Mystery shopping is just one way the FSA can spot poor practice in the market place. It remains a tactic that we will use in the right circumstances.”
